feat: only read from master (#623)

set options.masterOnly = true to enable the feature

pick from #622

lib/cluster.js

@@ -31,6 +31,8 @@ module.exports = function (OssClient) {
  }
 
  this.schedule = options.schedule || RR;
+ // only read from master, default is false
+ this.masterOnly = !!options.masterOnly;
  this.index = 0;
 
  const heartbeatInterval = options.heartbeatInterval || 10000;
@@ -180,6 +182,10 @@ module.exports = function (OssClient) {
 
  proto.chooseAvailable = function chooseAvailable() {
  if (this.schedule === MS) {
+ // only read from master
+ if (this.masterOnly) {
+ return this.clients[0];
+ }
  for (let i = 0; i < this.clients.length; i++) {
  if (this.availables[i]) {
  return this.clients[i];

test/node/cluster.test.js

@@ -230,6 +230,23 @@ describe('test/cluster.test.js', () => {
  this.store.removeListener('error', onerror);
  });
 
+ it('should MS always get from clients[0] when masterOnly === true', async function () {
+ mm(this.store, 'schedule', 'masterSlave');
+ mm(this.store, 'masterOnly', true);
+ mm(this.store.clients[1], 'get', 'mock error');
+ function onerror() {
+ throw new Error('should not emit error event');
+ }
+ this.store.on('error', onerror);
+
+ let res = await this.store.get(this.name);
+ res.res.status.should.equal(200);
+ res = await this.store.get(this.name);
+ res.res.status.should.equal(200);
+
+ this.store.removeListener('error', onerror);
+ });
+
  it('should get from clients[0] when clients[0] response 4xx ok', async function () {
  mm(this.store, 'schedule', 'masterSlave');
  mm.error(this.store.clients[0], 'get', 'mock error', { status: 403 });